Examination bed for NMR or tomodensitometry apparatus

ABSTRACT

An examination bed, notably for RMN or tomodensitometry, which includes a chassis, an examination plateau, and a mechanism for driving movement of the plateau with respect to the chassis and with respect to the apparatus wherein the moving mechanism includes a moving assembly with respect to the plateau and the chassis, elongated in its shape with one end being movable with respect to the chassis and whose other end is movable with respect to the plateau.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a medical examination bed notably for anuclear magnetic resonance (RMN) apparatus or a tomodensitometryapparatus. It is mainly used in the medical field where it is known thatpatients are made to lie down for non-invasive examinations with suchmachines.

2. Discussion of the Background

This type of examination is particular in that, in general, it takes along time to perform. To improve the comfort of the patient, it may thenbe necessary to ventilate the machine examination tunnel and toilluminate and conduct dialogue with the patient. In all cases, it isalso necessary to provide constant supervision of the latter. Indeed,patients going through such examinations are generally not in goodhealth and because of this, may be upset by the examination resulting inthem not feeling well. Under these conditions, they must be removed fromthe machine as quickly as possible. Under normal use, the insertion ofthe patient in the machine, on a plateau or a patient-support panel, isinitiated by the starting of motors. These motors may be electrical. Inthe case of RMN, it is desirable to have them installed as far aspossible from the examination tunnel so as not to interfere with theconsistency of the magnetic field, through metallic mass. But theindisposition of the patient may be caused by a cut-off of power. Thepatient will be aware of the cut-off of lighting, ventilation and ofsupervision means and will feel some anguish. Intervention or extract ofthe patient from the machine is then rendered difficult because theplateau manipulation motors will have falled because of the lack ofcurrent. But because of the mechanical ratios and the demultiplicationof these motors, it is unthinkable to attempt to turn the transmissionchain backward by hand.

In addition, examination beds may be used for entering patients into themachine and in some cases bringing them into their bedrooms whenexamination is over. Therefore, the beds can be disconnected from themachines. This requirement of bed mobility is incompatible with thenature of the examination being undertaken. Indeed, for suchexaminations, images, sectional views of parts of the patient's body aretaken. These images and sectional views correspond to particular partsof the patient's body. Therefore, it is necessary to identify and moveprecisely the part of the body to be imaged level with the imagerymeans. Consequently, when the bed is plugged into the machine, it isessential to bring the means for movement of the patient support panelon the bed to correspond exactly with the means for movement of thepanel in the machine. To avoid this difficulty, long panels have beenimagined, i.e. 3,50 meters long, still having one end engaged in the bedwhile the other is entered freely into the apparatus. It can bedemonstrated that although already long, this panel may beinsufficiently long to permit examination of the whole body. In thiscase the direction of patient presentation has to be inverted when theneed arises. In addition, a long bed is difficult to manipulate throughhospital corridors.

SUMMARY OF THE INVENTION

The present invention is designed to remedy the aforementioned drawbacksby proposing beds the plateau and means for driving the plateau includemeans to facilitate the manipulation of the patient. On the one hand,the plateau is rendered mobile to permit emergency withdrawals. Thisfeature cannot be provided without guidance of the plateau on itschassis and through the apparatus with offset setting particularitiesfor the position of the plateau with respect to the apparatus, suchparticularities being associated with a means of disengaging the plateaufrom the drive means ensuring its movement. These disengaging meanspermit exact replacement after emergency action. In addition, the mobilecharacter of the plateau makes it possible to reduce the cost of theequipment to be built it is simply necessary to build a bed chassis andseveral mobile plateaus placed in turn on the bed chassis in order to beinserted into the machine. This results in the fact that the preparationof patients to be put through examination no longer requiresimmobilizing the bed and even less so the examination apparatus. On theother hand, movement of plateau with respect to the chassis of the bedfor its insertion into the apparatus is ensured by using an auxiliary"differential" arm having a length similar to the length of the paneland/or chassis (2 meters) with one end of such arm driving the panelwhile the other rests on the chassis. In the invention, this is a way ofseparating the panel function, supporting the patient proper, from thepanel means of movement function (over a distance greater than theuseful length of the latter). The result is that the examination bedaccording to the invention has a conventional length adapted to itstransportation through hospital corridors.

The present invention relates to an examination bed, notably for RMN ortomodensitometry apparatus comprising a chassis, an examination plateauand means for moving the plateau with respect to the chassis and to anapparatus wherein the moving means comprise an assembly, elongated inits shape, that is mobile with respect to the plateau and chassis, oneend thereof is movable with respect to the chassis and the other end ismovable with respect to the plateau.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the reading of thedescription which follows and the examination of the accompanyingfigures. The figures are given for indicative reason and in no way limitthe invention. In the figures, the same references denote the sameelements. They show: FIG. 1: a schematic view of an examination bedaccording to the invention; FIG. 2: an exploded prespective view of themovable plateau of the examination bed according to the invention; FIG.3: a differential plateau manipulation arm; FIG. 4: a perspective viewof the guiding path of the plateau on its chassis and in the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a schematic sectional view of an examination bed according tothe invention. An RMN apparatus or a tomodensitometer 1 is provided toreceive, substantially in line with its axis of insertion 2, thepatient's body (not shown) supported by an examination bed in accordancewith the invention. This examination bed includes a chassis 4, a plateau5 and drive means 6 for moving the plateau with respect to the chassisand the apparatus. The invention is characterized by the drive means 6being a moving assembly of elongated shape. This moving assemblyincludes an arm 7, wherein one end 8 thereof can be moved with respectto the chassis and the other end 9 thereof can be moved with respect tothe plateau. Independent of the retention and supporting forces whichwill be explained subsequently, it can be understood that each point ofthe plateau can be moved with respect to any point of the chassis by alength equal to the sum of the useful travel 10 of end 8 with respect tothe chassis and of useful travel 11 end 9 with respect to the plateau.In addition, the arm causes the two end positions of the plateau to beoffset with respect to the center of the chassis. In the representationof FIG. 1, the plateau is at an end position suitable for preparationfor its insertion into the machine. In the other end position, plateau 5is completely advanced into machine 1 and the rear end 12 of the plateaumay be distant from the front end 13 of the chassis by a distancesubstantially equal to the length of arm 7.

In the example shown, the mobile assembly 6 includes two gear wheels 14and 15 rotating on shafts integral with the respective ends 8 and 9 ofthe arm. Gear wheel 14 bears on a rack 16 integral with the chassiswhile gear 15 bears on a rack 17 connected to the plateau. Pinons,preferably including teeth 18 and 19, are respectively rendered integralwith the gears 14 and 15. The pinons rotate about themselves about axescollinear with the wheel shafts. A continuous belt 20, preferablytoothed, is tensioned and meshes about the pinons. By a motor means,schematically shown by a ram 21, it is possible to push end 8 of arm 7.Rack 16 then causes gear 14 to turn driving pinon 18 and through belt20, driving pinon 19. Pinon 19 in turn drives the rack 17 of plateau 5in its movement. The longitudinal movement of rack 17 is limited by twostops 22 and 23 integral with plateau 5.

Consequently, plateau 5 moves with respect to end 9 of the arm by alength related to the movement of end 8 with respect to the chassis 4.The transformation ratio of the movements can be adapted by adjustingthe diameters of gears 14 or 15 and/or the diameters of pinons 18 and 19integral with these gears. In a preferred embodiment, the transformationratio is 1.

The embodiment could be achieved by other means. For instance, it wouldbe possible to obtain a moving assembly 6 with a triple jack, i.e. withat least three interleaved rods. A first rod would have one end attachedto the plateau and a third external rod would have one end, that isopposite the end of the first rod, attached to the chassis. Under theseconditions, it is equivalent to consider the second rod as forming themobile assembly and having a first end movable with respect to theplateau and a second end movable with respect to the chassis. Thissolution with hydraulic rams can be replaced by an equivalent screwsolution with at least three screws interleaved in one another.

In addition to the end elements, the intermediate elements, the rams orthe srews form the mobile assembly. When the intermediate elements aresingle, the mobile assembly is rigid and non-deformable. It correspondsto a rigid bar 7. If the intermediate elements are more numerous, forinstance if they include at least interleaved rods, the length of theintermediate element can be variable. In all cases, the invention alsooffers the advantage of making it possible to approach chassis 4 of theequipment 1 while leaving between these two parts a space 24 which canbe used for any patient preparation operation before the insertion ofthe patient in a machine. For instance it is possible for an operator toenter the space 24 to arrange the position of the patient's head on theplateau 5, in particular when the head is wearing part of themeasurement means needed for the examination to be undertaken, inparticular for RMN. Indeed, examination of the head must be carried outwhile making sure that the head cannot move during the examination.Therefore, it must be held to prevent it from moving in the image. Thisretention, which is unpleasant for the patient, must be undertaken atthe latest possible stage in order not to frighten the patient. Inpractice, it is carried out just before entry into machine 1. Withoutthe presence of mobile assembly 6, it would be necessary to insure thefullest possible useful travel of the plateau, to subsequently approachthe plateau as close as possible to the machine entry front.

The plateau 5 is further provided means of rendering it movable upon anemergency occurring. Schematically, FIG. 1 depicts plateau 5 retaining adrive rack 17 which meshes with mobile assembly 6 to move the plateau.The rack, maintained in its longitudinal movement by two stops 22 and 23integral with the plateau, can nevertheless sustain a verticalretraction, disengaging movement, tending to lift it. In this manner,the teeth of gear 15 of the mobile assembly escape the notches of rack17. In one example, the disengaging movement is obtained by means of aplate--cam 25 which maintains in slots, generally V- shaped, such as 26and 27, supporting shafts, respectively 28 and 29 of rack 17. Bysimplification, plate 25 is designed to move longitudinally by means ofhandles 30 or 31 located either side of the plate 5. It is horizontallymovable by means which will be described subsequently and serve the sameroll as the longitudinal windows such as 32 of plate 25, sliding alongdowels 33 of plateau 5.

By operating either of the handles, plate 25 is made to move to right orto left and drives upward the shafts 28 and 29. Under these conditions,the rack rises and escapes the teeth of gear 15. By working in thismanner, the means for moving plateau 5 are disengaged. It is thenpossible to slide the plateau on its supporting means. To facilitate theoperation of handle 30 or 31, such handle is matched with anotherhandle, respectively 34 or 35, integral with the plateau and has alongitudinal offset the value of which is approximately equal to theuseful displacement length of plate 25 with respect to the plateau. Inpractice, taking account of the depth of the teeth in gear 15 and rack17, and the inclination of the V of the slots 26 or 27 (approximately30°), it is possible to grasp in one hand both handles 30 and 34 or 31and 35. By closing the hand, disengaging of the rack 17 occurs. Theforce needed to attain this result is low because the rack weight isrelatively, light. In one example, this effort has been evaluated asbeing a force of approximately 2 kg force. Then, by maintaining the twohandles against one another, it is possible to displace plateau 5 in thedesired direction in order to extract machine 1.

FIGS. 2 to 4 show a particular example of the construction of plateau 5,moving assembly 6 and chassis 4. As an additional and essential feature,the examination bed according to this invention includes measuring means36 of the end position 8 of moving assembly 6 with respect to chassis 4.The means 36 may include a tachogenerator or resolvers mounted on gearshaft 18. Since the chassis is designed for being located in apredetermined space 24 of apparatus 1, and since the plateau is, in thenormal transportation position of the bed, at a predetermined endposition with respect to the chassis, by counting the number of turnseffected by the gear 14 or the pinon 18, it is possible to know whereany section of the plateau is located in the machine when it is advancedinto it. This arrangement offers the advantage of permitting highlytolerant positioning of plateau 5 in the machine. Finally, theconditions of the alignment of plateau 5 with the machine are no longercritical, even for measuring penetration into the machine.

By this method, it is possible to construct a plateau having a V-shapesection (FIG. 2), designed to slide on corresponding shaped guides inthe apparatus and in the chassis (FIG. 4). The apparatus and thechassis, in a preferred manner, include supporting areas numbered 37-38and 39-40 designed to receive bearing rollers such as 41-42 (FIG. 2) ofplateau 5. In a preferred example, the rollers are of epoxy glass fibercoated with rubber. This provides flexibility for the support and avoidssubjecting the patient to disagreable shaking. To ensure the guidance ofthe plateau in the machine and the chassis of the bed, these includeinclined planes, respectively 43-44 and 45-46 which bear against rollerssuch as 47 of the plateau 5. In practice, the angle of inclination ofthe inclined plates is around 30°. This is a compromise between theguidance efficiency to be obtained and the limits at which therubberized linings come off the glass rollers. In one example, tosupport the plate, approximately two dozen rollers such as rollers 41-42are used. For the guide, approximately half a dozen are placed on eitherside. The plateau can also include side handles such as 48 to 51,regularly distributed either side of the panel. With these handles, theplateau can be grasped and placed on a gurney for wheeling through thehospital. In one preferred embodiment, the disengaging device on therack is slightly different. Rack 17 is flushed-fitted into a groove 51inside the plateau. It is inserted between the two stops including stop23 which is visible, integral with the plateau. Either side of the rack17, in groove 51, are entered on edge, the two plates 25 and 52 beingdesigned to play the same part and ensure symmetry of the lifting forceof the rack 17. Handle 31 is designed to move longitudinally the twoplates 25 and 52 at the same time. With respect to FIG. 1, the plateguiding device with respect to the plateau 5 has been modified. Theplates are each provided with a shoe on their lower edge, such as 53 tobear beneath plateau 5 and thus play the same part as dowels 33 in holes32. In a preferred manner, cams 26 and 27 have, at the edges and at thecenter of the V, flats forming positions of rests for the lifting forceand maintain rack 17. Accordingly, the low and high positions of therack are mechanically stable. The central flat on the cams, i.e. flat54, is designed to apply pressure from top to bottom to the supportingshafts, i.e. shaft 55 of the rack to prevent, since the weight of therack is low, that it lifts alone under the drive effect of gear 15. Inone example, rather than two sets 26-27 of slots-cams, plates 25 and 52include approximately ten of them. In this manner, there is no need toexcessively rigidify rack 17.

Mobile assembly includes arm 7 in which the gears 14 and 15 move ateither end. Arm 7 is in the form of a box provided with two openings,for instance opening 57 to permit gears 14 or 15 protrude beyond therespectively lower surface 58 and upper surface 59 of box 7. The armalso has a front roller 60 to permit its bearing in machine 1 whenengaged in it. For this purpose, the input edge of the machine has achamfer 61 (FIG. 1 and 4) to receive the roller and permit the insertionof the arm into a groove 62, provided in the machine tunnel. In thisway, during the greater part of its transfer, the arm rests partly onrack 16 through gear 14 and partly in groove 62 through roller 16. Atthe exit of chassis 4 there is connecting block 63 designed to bearunder boxed section 7 while head 9 of arm 7 crosses space 24. Taperedends 64 and 65 of connecting block 63 cater for alignment faults betweenthe machine. It is intended to provide the side edges of arm 7 withblocks such as 66 or 67, preferably of polytetrafluoroethylene to bearon the vertical sides of the grooves in chassis 4 and of machine 1. Theoverall height of the arm is calculated so that the arm can be housedwithin grooves 51 and 61 or between racks 16 and 17, without applyingany supporting force to the plateau.

The bed and/or chassis according to the invention can also be providedwith the aforementioned attached devices.

In addition, and by preference, the bed is adjustable as to height inorder to suit all different machines and to facilitate the loading ofany nonbedridden patient enabling him or her to sit on the plateau nearthe ground. The elevation of the bed is caused by the rotation of thelegs of an X. In a preferred embodiment, base 68 of one of the legs,i.e., leg 69 is held fixed with respect to machine 1 while the base ofthe other leg can slide toward base 68 under the effect of motor 71.Under these conditions, a space or deviation 24 between the bed and themachine varies as a function of the bed's height in order to facilitate,even more in the low position, passage of the operator during risingmovement. The bed is put through rotational movement to reduce the gapseparating it from the machine.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedtherein.

We claim:
 1. An examination bed, notably for a NMR or tomodensitometry apparatus, which comprises:a chassis; an examination plateau; moving assembly means for moving the plateau with respect to the chassis and said apparatus; and means for translating said moving assembly means with respect to said plateau, said chassis and said apparatus, said moving assembly means being elongated in shape, a first end of said moving assembly means including means for mechanically connecting said moving assembly means to said chassis and including means for moving said first end in translation with respect to said chassis and a second end of said moving assembly means including means for providing mechanical motion connection of said moving assembly means to the plateau, and means for moving said second end in translation with respect to said plateau wherein said means for translating said moving assembly means is connected to said moving assembly means.
 2. A bed according to claim 1, wherein said moving assembly means includes an arm having a predetermined and fixed length and having, at said first and second ends of said moving assembly means, mobile drive means for moving said arm, respectively, in translation with respect to said chassis and said plateau with respect to said arm.
 3. A bed according to claim 1 or 2, wherein said moving assembly means includes coupling means so that movements with respect to said first and second ends are mechanically dependent.
 4. A bed according to claim 3, wherein said arm includes first and second drive gears which mesh with first and second racks respectively connected to said chassis and to said plateau.
 5. A bed according to claim 4, wherein said means for moving said plateau with respect to said chassis includes a belt having teeth for meshing with said drive gears.
 6. A bed according to claim 3, wherein said coupling means are such that the ratio of movement of said plateau with respect to said moving assembly means is one to one and the ratio of movement of said moving assembly means with respect to said chassis is one to one.
 7. A bed according to claims 1 or 2, wherein said chassis includes, at an end near said apparatus, a coil provided with two cones opposed by an apex.
 8. A bed according to claim 2, wherein said arm includes a roller positioned in an area adjacent said apparatus so as to form a support point of said arm upon positioning of said arm in said apparatus.
 9. A bed according to claim 3, wherein said apparatus and said chassis include grooves for receiving said arm and wherein said arm includes side blocks for guiding said arm between sides of said grooves.
 10. A bed according to claims 1 or 2, wherein said moving assembly means includes means for measuring the position of said plateau with respect to said apparatus and while simutaneously measuring the position of an end of said moving assembly means connected to said chassis. 